A Primer on Psychiatric Disorders, part 3

Recently I came across a fascinating article in the science journal Nature about new discoveries in the genetics of breast cancer. The new research identified four distinct genetic subtypes, one of which appears closely related to ovarian cancer (a surprising link). If there’s a common cause, perhaps the treatments for ovarian cancer can be used successfully with certain breast cancers.

We can always hope for something comparable with psychiatric disorders. As a general rule, the better the causes of a disease are understood, the more effective the treatments will be.

Science knows much less about the etiology (causes) of mental illness, partly because much less is known about the brain. That’s one reason the DSM (psychiatry’s diagnostic manual) has avoided the subject and stuck to descriptions of symptomatology.

It has been established that there is a genetic component to major mental illnesses. One piece of evidence is twin studies. Researchers compare sets of identical and fraternal twins. If a disorder has a genetic basis, there will be a higher concordance (same trait in both members of a pair) among identicals than fraternals.

Here’s a chart of concordance for various mental disorders (you may see different percentages based on different studies — these are just what I found):

Comparison of Illnesses

Disorder

Concordance: Identical twins ss

Concordance: Fraternal twins

Schizophrenia

40%

10%

Depression

50%

15%

Bipolar disorder s

40%

10%

We can compare that to other common illnesses:

Breast cancer

30% s

10%

Coronary heart disease s

40%

10%

Remember, we’re not talking about inheriting a disease — we’re talking about vulnerability to that disease. Environment will always play a key role. Still, if there is a genetic component to developing schizophrenia, bipolar disorder, etc., then there’s hope for new treatments that may surpass the effectiveness of anything we have now.